Rectangular or box-shaped ducts are extensively utilized in heating and ventilating systems to distribute heated or cooled air throughout a structure. These ducts are commonly formed from differing gauges of sheet metal in sections of predetermined lengths, which are then connected to one another to form a continuous duct for distributing air.
Typically, each section of duct is formed by bending two pieces of sheet metal of the desired length at a 90° angle. One edge of each piece is formed to include a longitudinally extending groove, forming thereby the female portion of the seam, while the other longitudinal edge of each piece is bent over along its length to form thereby the male portion of the seam. The two pieces are then assembled by inserting the male portion of each piece into the female portion, leaving an edge extending beyond the joint from the female portion. This extended edge must then be bent over to lock the seam. One industry standard example of such a seam is a ‘Pittsburgh’ lock or seam.
A seam closing tool is utilized to complete the sealing process by bending over the extended edge of the female portion. Known seams, such as the Pittsburgh seam, include an extended edge which extends approximately perpendicularly to its final, sealed position. Consequently, the seam closing tool must employ a plurality of rollers to gradually bend, or form, the extended edge over to its final sealed position, each of the plurality of rollers bending the extended edge over to a greater degree until the final sealing position is attained. It is also known to utilize either a manual or pneumatically actuated hammer to bend or form over the extended edge of the female portion.
While these known sealing systems are successful to a degree, they suffer from several logistical problems. Firstly, the multi-roller seam closing tool cannot completely seal the entire length of a given seam at those locations adjacent the end of the seam. This inability to completely seam the length of the seam is due to the graduated sealing angles inherent in each of the plurality of rollers of the seam closing tool. That is, it is the last of the rollers which has the most severe sealing angle and accomplishes the final sealing operation of the seam closing tool, however the last roller is preceded by all of the other rollers and, therefore, will not be permitted to reach or affect the last few feet or inches of the seam. Hammering will thus be necessary to finish the complete seal of the seam.
Similarly, the manual or pneumatic hammering of the seam in its entirety is highly labor intensive and quite loud, oftentimes requiring ear protection for the operators who assemble the finished duct work. Moreover, the time and effort extended on hammering the extended edge of the female portion over to seal the seam, can substantially increase the time and expense of any duct fabrication and installation job, typically by as much as 50% or more.
With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a seam closing apparatus which overcomes the above-described drawbacks while maximizing effectiveness and flexibility in the assembling process.